Effect of interatrial block on left atrial function

Interatrial block produces prolonged P-waves due to conduction delay mainly in the Bachmann bundle, the most direct route from right to left atrium. It is prevalent in patients over age 60 with its main clinical significance its association with eventual atrial fibrillation and/or flutter. Having demonstrated a mean delay in the onset of active left ventricular filling of 37 msec, we defined the electromechanical abnormality further by measuring left atrial volume at key points in the atrial cycle to produce 10 measurements of left atrial function. Compared to the normal left atrium, interatrial block is correlated with a large, poorly contractile left atrium with a delayed and markedly reduced contribution to left ventricular filling and the kinetic energy with which atrial systole propels blood.